Journal of clinical monitoring and computing
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J Clin Monit Comput · Feb 2014
A pilot study quantifying the shape of tidal breathing waveforms using centroids in health and COPD.
During resting tidal breathing the shape of the expiratory airflow waveform differs with age and respiratory disease. While most studies quantifying these changes report time or volume specific metrics, few have concentrated on waveform shape or area parameters. The aim of this study was to derive and compare the centroid co-ordinates (the geometric centre) of inspiratory and expiratory flow-time and flow-volume waveforms collected from participants with or without COPD. ⋯ A comparison of airflow waveforms show that in COPD, the breathing rate is faster (17 ± 4 vs 14 ± 3 min(-1)) and the time to reach peak expiratory flow shorter (0.6 ± 0.2 and 1.0 ± 0.4 s). The expiratory flow-time and flow-volume centroid is left-shifted with the increasing asymmetry of the expired airflow pattern induced by airway obstruction. This study shows that the degree of skew in expiratory airflow waveforms can be quantified using centroids.
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To control the three components of general anesthesia (hypnosis, analgesia, and neuromuscular blockade), an automated closed-loop, anesthesia-drug delivery system (McSleepy) was developed. Bispectral index was used as the control variable for hypnosis, the analgoscore for analgesia, and phonomyography for neuromuscular blockade. McSleepy can be used to control the induction, maintenance and emergence from general anesthesia. ⋯ Preliminary results of 15 patients are presented in this paper. Evaluation of McSleepy was done through an assessment of its clinical performance and using Varvel's performance indices. The system was found to be clinically useful by providing good precision in drug administration and reliable results for the duration of a general anesthesia.
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J Clin Monit Comput · Feb 2014
Observational StudyCardiac output assessed by non-invasive monitoring is associated with ECG changes in children with critical asthma.
The primary aim of this study was to determine changes in CI and SI, if any, in children hospitalized with status asthmatics during the course of treatment as measured by non-invasive EC monitoring. The secondary aim was to determine if there is an association between Abnormal CI (defined as <5 or >95 % tile adjusted for age) and Abnormal ECG (defined as ST waves changes) Non-invasive cardiac output (CO) recordings were obtained daily from admission (Initial) to discharge (Final). Changes in CI and SI measurements were compared using paired t tests or 1-way ANOVA. ⋯ In children that required a prolonged course of treatment, there was also a significant decrease in SI. Abnormal CI at Initial CO recording was associated with ST waves changes on ECG during hospitalization. Future studies are required to determine whether non-invasive CO monitoring can predict which patients are at risk for developing abnormal ECG.
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J Clin Monit Comput · Feb 2014
Bench test assessment of mainstream capnography during high frequency oscillatory ventilation.
To assess the feasibility, stability and predictability of pCO2 measurement (PETCO2) using a main stream capnograph in a high frequency oscillatory ventilation circuit. A commercially available capnograph was mounted into a high frequency oscillatory ventilator patient circuit, adjustable CO2 flow was introduced into an artificial lung and the output of the CO2 sensor assessed under varying ventilator settings. Influence of oxygen content, pressures, heat and moisture were recorded. ⋯ From this bench test, we conclude it is feasible to measure PETCO2 using a main stream capnograph during high frequency oscillatory conditions, these measurements were stable during the experiment. Changes in CO2 production or output can be detected. The system may prove to be of clinical value, but further in vivo measurements are warranted.
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Although feedback control and automation has revolutionized many fields of human activity, it has yet to have a significant impact on healthcare, particularly when a patient is in the loop. Although there have been a number of studies concerned with closed-loop control of anesthesia, they have yet to have an impact on clinical practice. ⋯ Concepts such as modelling for control, feedback and uncertainty, robustness, feedback controller such as proportional-integral-derivative control, predictive control and adaptive control are briefly reviewed. Finally we discuss the safety issues around closed-loop control and discuss ways by which safe control can be guaranteed.